Putting weights on speakers?

mglik-

Hi millercarbon,
Thanks for the thoughtful post.
The original design of the Tetra 606 had exactly what you suggest with struts going from the speaker top to the bass cabinet.

Yeah that one's a no-brainer. They will never admit this but its clear to me they got rid of the struts for aesthetics not sonics. 

I admire your deep knowledge and application in your posts and, certainly, your system. I see the very nice concrete block under your TT. Very attractive.

Thanks. The entire rack is my own design. I made the molds to cast the curves. The columns are filled with concrete. Its a modular design, the columns and shelves being bolted together on site. Otherwise the whole rack at 700+ lbs would be too hard to move. 

The top and bottom shelves of cast concrete incorporate sand beds. Concrete and granite are nice and dense and stiff but not very well damped and have a nasty habit of ringing. A layer of sand between them damps the majority of the ringing. Incredibly high damping factor BDR Shelf and Cones takes care of the rest.

The lesson for your situation is its the same but different. Its the same because in both cases, rack and speaker, we want a rigid stable platform. Mass resists motion improving dynamics but releases it back into where we don't want it at rates determined by how stiff and damped the mass is. Stiffness improves transient response but without mass and damping it just vibrates noisily like a tuning fork. Damping lowers the noise floor but sounds lifeless and dull unless combined with mass and stiffness.

Think the Rouge Fitness vest plates will do the job of mass loading nicely. They are almost exactly the right dimensions. 4 plates would only be 1 inch and 4/16ths and they are black.

If you experiment with the vest plates, etc, and listen the combined effects of mass, stiffness and damping will become clear. You will be able to hear it. You will even be able to fine tune your results by tweaking even small things like putting a layer of material between the plate and the speaker. Sorbothane, vinyl, leather, fabric, etc.

Have you thought of mass loading your speakers? My speaker designer didn’t like it when I told him but did respect my ears.

Well, they never do. Anyone designing a speaker knows everything I just explained, and then some. They tried all this same stuff, and then some. They played with wood species, thicknesses, shape, different gasket materials between the driver and baffle, on and on. Then they balance all that against cost of production and consumer acceptance. Finally they have to try and convince buyers the resulting pile of compromises is in fact the absolute best anyone could ever do, period, no matter what. For some strange reason a lot of people buy into this. 

So of course they are not going to like you messing with their masterpiece. At the same time though they want you as a customer. Thus the respect for your ears. Try telling them you sold their masterpiece for Tekton Moabs, see how much they respect your ears then! (That's a joke, btw. But not really.) ;) 

My last speakers were Talon Khorus, and I did think of mass loading them but their tapered shape made it hard to do anything but put more mass in the base, where they were already pretty darn heavy. https://systems.audiogon.com/systems/8367
The Tekton Moabs that are due in a week or so may or may not be another story. Will have to check them out and see. But probably what will happen is, I have gone so far beyond mass loading it would seem like going backwards to be doing that now.

Look closely at the design of your speaker. Notice they have a very thick strong and heavy baffle. Its open, but that is their little design hook. Open baffle is kind of a thing lately. Its an opportunity to learn about the tradeoffs of loudspeaker design, I guess.

The change you heard is exactly what I would predict, even without knowing what speakers or how they are designed. Notice mahgister has great results from adding even more mass to his. Whatever they are. Nobody asks mahgister. Interesting....

Basic Newtonian physics, F=MA, force equals mass times acceleration. Our goal is to have the driver move the air while the speaker cabinet remains fixed, so all the sonic energy goes into the air. Obviously if the speakers are just hanging from strings in the air they are going to move a lot, much of the energy gets wasted moving them back and forth instead of moving air, and they sound like you know what. 

That is the ultimate open baffle, you may like it. I can imagine the superlatives. Among them will not be dynamics. All the dynamics will be sucked out. Adding mass to the drivers will restore the dynamics. And detail. Tremendous amount of detail is lost in cabinet vibrations.

So you want to add mass. They already added as much as they could with that big thick front baffle and a woofer cabinet about ten times as big as it needs to be. Still the open baffle design forces them to eliminate the #1 easiest and best thing they could do to improve dynamics and detail and that is reinforce the baffle with a cabinet with sides and back. Oh well. 

So this is your challenge. How to add mass without compromising the sonic and aesthetic integrity of the design.

In a word, you can't. Sorry. But you just can't. Mass would be most effective on top. But you can't put it there because there is no top. Mass would be second most effective behind the baffle. But you can't put it there because baffle shape and size affects frequency response. You could install some struts running from the top corners down to the back corners of the sub cabinet. That would effectively mass load and stiffen the baffle but look like absolute crap.

The closest I can think of would be to make a cast concrete slab several inches thick and shaped to sit on top of the bass cabinet. If done right, tapered and painted, it would blend almost seamlessly with the bass cabinet. To get some idea what cast concrete can be, look at my turntable rack. https://systems.audiogon.com/systems/8367

This would be a bit of a project. But if you put in the time you could make it look good enough to keep the wife happy. Maybe. I know all about audio. Women, on the other hand.....